During the sweltering summer, people often seek cold drinks and ice cream at convenience stores to cool off. After wiping away sweat and sipping a refreshing beverage, they head home to turn on the air conditioning. This surge in demand for cooling products is known as the 'heat wave effect.'
In Japan, the impact of the heat wave effect on summer product sales has become evident. An analysis by the Japan Meteorological Association and market research firm Intage revealed that for every 1 degree Celsius increase in weekly average temperature, sales of sports drinks, fruit juices, and ice cream tend to rise by 6-8%. The demand for cold noodles also increased, likely due to the heat. Sales of sunscreen, antiperspirants, and health drinks also saw a rise of 6-12%. But does the heat wave effect continue to expand as temperatures rise?
According to a study by advertising agency Dentsu and location data firm Unruly, outdoor activity rates began to decline around 31 degrees Celsius. The analysis, based on movement data from 47 prefectures between June and September last year, defined outdoor activity as moving more than 500 meters from home, excluding rainy days.
The two companies further compared outdoor activity rates on Saturdays when temperatures were below 30 degrees and above 35 degrees. They found that on days exceeding 35 degrees, outdoor activity rates were lower from 9 a.m. to 4 p.m., but increased after 6 p.m. Specifically, the outdoor activity rate at 2 p.m. was 1.9 percentage points lower on days above 35 degrees compared to those below 30 degrees, while the rate at 7 p.m. was 1.3 percentage points higher. Dentsu and Unruly concluded that when temperatures exceed 35 degrees, people tend to avoid outdoor activities during the hottest part of the day, often rescheduling plans for the evening.
When temperatures surpass 35 degrees, not only do outdoor activities decrease, but consumer spending also begins to decline. A joint analysis by the Nihon Keizai Shimbun (Nikkei) and Dai-ichi Life Research Institute examined average daily household spending in ten major cities during weekdays in July and August from 2023 to 2025. They found that spending started to decrease when temperatures exceeded 35.7 degrees, which Nikkei identified as the tipping point where the heat wave effect turns into a contraction in consumer spending.
Sports drinks, typically popular during hot weather, have seen a decline in sales. While they usually sell well as temperatures rise, market research firm True Data reported that sales have struggled since the record heat wave in 2023. With heatstroke warnings leading to the cancellation of outdoor activities and sports events, opportunities to consume sports drinks have diminished. Additionally, a drop in supermarket visitors during peak heat hours has hindered sales of milk and large-volume beverages. True Data explained that since a certain percentage of store visitors typically make purchases, a decrease in visitors directly impacts sales.
Conversely, some products have seen increased sales due to reduced outdoor activities. Ice cream, for instance, has benefited from the heat, as people are more likely to seek it at home rather than outdoors. Traditionally, it was believed that ice products with higher ice content would sell better in hot weather, but the trend has shifted as people stay indoors. In contrast, outdoor-friendly frozen treats have struggled.
As temperatures approach 40 degrees, consumer demand has shifted toward products that provide immediate cooling relief. An analysis by NTT Docomo of purchasing data in the Kanto region from April to September 2024 found that the purchase of cooling sprays, neck coolers, and cooling towels increased significantly. When temperatures exceeded 30 degrees, purchases nearly doubled compared to a baseline of 25 degrees, and approached eight times as temperatures neared 40 degrees. In the food sector, sales of 'ice slurry' beverages, which mix fine ice particles with liquids to lower body temperature, have surged. According to retail sales data from RDS-POS, sales of products labeled 'ice slurry' in June 2024 surpassed last summer's peak.
During a five-day stretch from July 21 to 25, when temperatures exceeded 40 degrees in the Tokai region, sales of frozen beverages at Lawson convenience stores increased 2.2 times compared to the previous month. In Aichi Prefecture, sales surged by 3.5 times. Sales of frozen treats also rose by 1.5 times. The top-selling frozen beverage was barley tea, followed by sports drinks. While traditional sports drinks struggled due to canceled outdoor activities, the extreme heat drove demand for frozen forms.
Although consumer spending began to decline when temperatures exceeded 35.7 degrees, overall spending to cope with the heat has increased this summer. According to Daikoku Data Bank, higher-than-average temperatures in Tokyo are estimated to have raised household spending by 21.15 billion yen (approximately $182 million). This includes 8.481 billion yen on food and beverages, 4.3 billion yen on cooling appliances, and about 2 billion yen on health and medical expenses. These expenses on beverages, cooling devices, and medical costs are considered unavoidable 'heat costs' for households. However, spending on clothing has decreased due to fewer outdoor opportunities, and gas expenses have also dropped as people avoid cooking at home. Overall, some analysts suggest that the heat continues to drive consumer spending in Japan. Daiwa Institute of Research estimates that for every 1 degree increase in average monthly temperature, nominal household spending rises by 0.3% in July and 0.2% in August, estimating the heat wave effect from July to September last year at 239.7 billion yen.
As unavoidable cooling costs rise due to the heat, households are cutting back on travel and leisure expenses. A survey by market research firm Japan Information found that 58.5% of respondents aged 20 to 69 reported that they found it difficult to reduce electricity costs, while 46.2% indicated they would cut back on travel and leisure spending. Additionally, 56.5% noted that the heat had reduced their shopping and outdoor activity frequency. Ultimately, the heat wave effect does not endlessly expand with rising temperatures. Beyond a certain point, outdoor activities and consumer spending decline, with expenditures concentrating on products that help endure the heat.
* This article has been translated by AI.
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